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Bernhardsson, Magnus
Publications (9 of 9) Show all publications
Schilcher, J., Bernhardsson, M. & Aspenberg, P. (2019). Chronic anterior tibial stress fractures in athletes: No crack but intense remodelling. Scandinavian Journal of Medicine and Science in Sports, 29(10), 1521-1528
Open this publication in new window or tab >>Chronic anterior tibial stress fractures in athletes: No crack but intense remodelling
2019 (English)In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 29, no 10, p. 1521-1528Article in journal (Refereed) Published
Abstract [en]

PURPOSE: Delayed healing of anterior tibial stress fractures in athletes is related to high tensional forces acting across a putative fracture gap. These forces lead to crack propagation and create strains that exceed tissue differentiation thresholds for new bone to form in the gap. The "dreaded black line" is a radiographic hallmark sign of stress fractures considered to represent a transverse fracture gap. However, whether a fracture gap truly exists at the microscopic level remains unclear. The aim of this study was to describe the area of the "dreaded black line" microscopically and to identify signs of delayed healing.

METHODS: Between 2011 and 2016 we included seven athletes with chronic anterior mid-shaft tibial stress fractures. The fracture site was excised as a cylindrical biopsy. The biopsy was evaluated with micro-CT and histology. The formation of new bone in the defect was evaluated radiographically.

RESULTS: The "dreaded black line" seen on preoperative radiographs in all patients could not be seen on the microscopic level. Instead, the area of the putative crack showed widened resorption cavities, lined with active osteoblasts, and surrounded by immature bone. This area of intense remodelling seemed to create a false impression of a fracture line on radiographs. Complete cortical continuity was restored at the biopsy site at median eight months (range six to 13 months).

CONCLUSION: Tibial stress fractures in athletes normally show no fracture defect, but a region of increased remodelling. The healing process is already ongoing but seems mechanically insufficient. 

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
Stress fracture, fracture healing, histology, tibia
National Category
Orthopaedics
Identifiers
urn:nbn:se:liu:diva-157071 (URN)10.1111/sms.13466 (DOI)000488616400008 ()31102562 (PubMedID)
Funder
Region ÖstergötlandSwedish Research CouncilSwedish National Centre for Research in Sports
Available from: 2019-05-27 Created: 2019-05-27 Last updated: 2019-11-14
Amirhosseini, M., Bernhardsson, M., Lång, P., Andersson, G., Flygare, J. & Fahlgren, A. (2019). Cyclin-dependent kinase 8/19 inhibition suppresses osteoclastogenesis by downregulating RANK and promotes osteoblast mineralization and cancellous bone healing.. Journal of Cellular Physiology, 234(9), 16503-16516
Open this publication in new window or tab >>Cyclin-dependent kinase 8/19 inhibition suppresses osteoclastogenesis by downregulating RANK and promotes osteoblast mineralization and cancellous bone healing.
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2019 (English)In: Journal of Cellular Physiology, ISSN 0021-9541, E-ISSN 1097-4652, Vol. 234, no 9, p. 16503-16516Article in journal (Refereed) Published
Abstract [en]

Cyclin-dependent kinase 8 (CDK8) is a mediator complex-associated transcriptional regulator that acts depending on context and cell type. While primarily under investigation as potential cancer therapeutics, some inhibitors of CDK8-and its paralog CDK19-have been reported to affect the osteoblast lineage and bone formation. This study investigated the effects of two selective CDK8/19 inhibitors on osteoclastogenesis and osteoblasts in vitro, and further evaluated how local treatment with a CDK8/19 inhibitor affects cancellous bone healing in rats. CDK8/19 inhibitors did not alter the proliferation of neither mouse bone marrow-derived macrophages (BMMs) nor primary mouse osteoblasts. Receptor activator of nuclear factor κΒ (NF-κB) ligand (RANKL)-induced osteoclastogenesis from mouse BMMs was suppressed markedly by inhibition of CDK8/19, concomitant with reduced tartrate-resistant acid phosphatase (TRAP) activity and C-terminal telopeptide of type I collagen levels. This was accompanied by downregulation of PU.1, RANK, NF-κB, nuclear factor of activated T-cells 1 (NFATc1), dendritic cell-specific transmembrane protein (DC-STAMP), TRAP, and cathepsin K in RANKL-stimulated BMMs. Downregulating RANK and its downstream signaling in osteoclast precursors enforce CDK8/19 inhibitors as anticatabolic agents to impede excessive osteoclastogenesis. In mouse primary osteoblasts, CDK8/19 inhibition did not affect differentiation but enhanced osteoblast mineralization by promoting alkaline phosphatase activity and downregulating osteopontin, a negative regulator of mineralization. In rat tibiae, a CDK8/19 inhibitor administered locally promoted cancellous bone regeneration. Our data indicate that inhibitors of CDK8/19 have the potential to develop into therapeutics to restrict osteolysis and enhance bone regeneration.

Keywords
CDK8, RANK, osteoblasts, osteoclasts
National Category
Cell and Molecular Biology Medicinal Chemistry
Identifiers
urn:nbn:se:liu:diva-154927 (URN)10.1002/jcp.28321 (DOI)000470174200186 ()30793301 (PubMedID)
Note

Funding agencies: Vetenskapsradet [521-2013-2593, 2016-06097, K2015-99x-10363-23-4, 2016-01822]; Swedish Research Council

Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2019-07-03
Bernhardsson, M., Dietrich, F., Tätting, L., Eliasson, P. & Aspenberg, P. (2019). Depletion of cytotoxic (CD8+) T cells impairs implant fixation in rat cancellous bone. Journal of Orthopaedic Research, 37(4), 805-811
Open this publication in new window or tab >>Depletion of cytotoxic (CD8+) T cells impairs implant fixation in rat cancellous bone
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2019 (English)In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 37, no 4, p. 805-811Article in journal (Refereed) Published
Abstract [en]

As cytotoxic (CD8(+)) T cells seem to impair shaft fracture healing, we hypothesized that depletion of CD8(+) cells would instead improve healing of cancellous bone. Additionally, we also tested if CD8-depletion would influence the healing of ruptured Achilles tendons. Rats received a single injection of either anti-CD8 antibodies or saline and put through surgery 24 h later. Three different surgical interventions were performed as follows: (1) a drill hole in the proximal tibia with microCT (BV/TV) to assess bone formation; (2) a screw in the proximal tibia with mechanical evaluation (pull-out force) to assess fracture healing; (3) Achilles tendon transection with mechanical evaluation (force-at-failure) to assess tendon healing. Furthermore, CD8-depletion was confirmed with flow cytometry on peripheral blood. Flow cytometric analysis confirmed depletion of CD8(+) cells (p amp;lt; 0.001). Contrary to our hypothesis, depletion of CD8(+) cells reduced the implant pull-out force by 19% (p amp;lt; 0.05) and stiffness by 34% (p amp;lt; 0.01), although the bone formation in the drill holes was the same as in the controls. Tendon healing was unaffected by CD8-depletion. Our results suggest that CD8(+) cells have an important part in cancellous bone healing.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
bone healing; cancellous; tendon healing; cytotoxic T cells; CD8 depletion
National Category
Orthopaedics
Identifiers
urn:nbn:se:liu:diva-157559 (URN)10.1002/jor.24246 (DOI)000467082100001 ()30737834 (PubMedID)2-s2.0-85062344231 (Scopus ID)
Note

Funding Agencies|Swedish Research Council [2031-47-5]; AFA insurance company EU 159 7th framework program [FP7/2007-2013, 279239]; Linkoping 160 University

Available from: 2019-06-22 Created: 2019-06-22 Last updated: 2019-06-25Bibliographically approved
Bernhardsson, M. & Aspenberg, P. (2018). Abaloparatide versus teriparatide: a head to head comparison of effects on fracture healing in mouse models. Acta Orthopaedica, 89(6), 674-677
Open this publication in new window or tab >>Abaloparatide versus teriparatide: a head to head comparison of effects on fracture healing in mouse models
2018 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 89, no 6, p. 674-677Article in journal (Refereed) Published
Abstract [en]

Background and purpose - Teriparatide accelerates fracture healing in animals and probably in man. Abaloparatide is a new drug with similar although not identical effects on the teriparatide receptor. Given at 4 times the teriparatide dose in a human osteoporosis trial, abaloparatide increased bone density more than teriparatide, and both reduced fracture risk. We investigated in mice whether abaloparatide stimulates fracture healing, and if it does so with the suggested dose effect relation (4:1). Patients and methods - In a validated mouse model for metaphyseal healing (burr hole with screw pull-out), 96 mice were randomly allocated to 11 groups: control (saline), teriparatide or abaloparatide, where teriparatide and abaloparatide were given at 5 different doses each. In a femoral shaft osteotomy model, 24 mice were randomly allocated to 3 groups: control (saline), teriparatide (15 mu g/kg) or abaloparatide (60 mu g/kg). Each treatment was given daily via subcutaneous injections. Results were evaluated by mechanical testing and microCT. Results - In the metaphyseal model, a dose-dependent increase in screw pull-out force could be seen. In a linear regression analysis (r = 0.78) each increase in ln(dose) by 1 (regardless of drug type) was associated with an increase in pull-out force by 1.50 N (SE 0.18) (p amp;lt; 0.001). Changing drug from teriparatide to abaloparatide increased the force by 1.41 N (SE 0.60; p = 0.02). In the diaphyseal model, the callus density was 23% (SD 10), 38% (SD 10), and 47% (SD 2) for control, for teriparatide and abaloparatide respectively. Both drugs were significantly different from controls (p = 0.001 and p = 0.008), but not from each other. Interpretation - Both drugs improve fracture healing, but in these mouse models, the potency per mu g of abaloparatide seems only 2.5 times that of teriparatide, rather than the 4:1 relation chosen in the clinical abaloparatide-teriparatide comparison trial.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2018
National Category
Orthopaedics
Identifiers
urn:nbn:se:liu:diva-153697 (URN)10.1080/17453674.2018.1523771 (DOI)000453932600015 ()30334479 (PubMedID)
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-05-02
Bernhardsson, M. (2018). Healing Processes in Cancellous Bone. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Healing Processes in Cancellous Bone
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Most of what is known about the biological response during fracture healing comes from numerous animal studies with shaft fractures in the long bone. However, most patients suffer from fractures closer to the ends of the long bones, in the hip, or in the vertebrae. These types of fractures mainly involve cancellous bone, while shaft fractures concern cortical bone. Compared to cortical bone whose structure is dense and compact, cancellous bone is of spongy and porous structure. A growing number of studies point towards that cortical and cancellous bone heal differently. To even this imbalance in knowledge between these two types of bone tissue, further studies in cancellous bone are justified.

In this thesis we delved into the quiet unknown processes behind cancellous bone healing.

In the first study we characterized and compared two models for cancellous bone healing in mice and rats: the first model can be used to analyze the morphology and morphometry of the regenerating bone; the second model can measure the mechanical properties of cancellous bone. The two models correspond in their developing patterns during the first week before they diverge. This suggests that these models can be utilized together to evaluate the initial healing in cancellous bone. Furthermore, we saw in the drill hole model that the bone formation is strictly restricted to the traumatized region, with a distinct interface to the adjacent uninjured tissue.

The second study characterized the cellular response during the initial healing phase in cancellous bone. The focus was to follow the spatial location of inflammatory and osteogenic cells over time in a cancellous bone injury. In contrast to shaft fractures (cortical bone), where healing is described as sequential events where inflammatory cells are the first to arrive to the trauma before osteogenic cells are recruited and initiate healing, we could see how inflammatory and osteogenic cells appeared early, simultaneously after a cancellous bone injury. This study showed that cancellous bone differs from how fracture healing is normally described.

In the third study we explored the role of a subpopulation of lymphocytes (CD8 positive cells), earlier studied in shaft fractures. We wanted to see how their absence would affect the healing in a cancellous bone injury. Without CD8+ cells, cancellous bone healing was impaired as expressed via poorer mechanical properties of the regenerated bone tissue.

The fourth and last study issued the influence of uninjured bone marrow on cortical bone healing. We developed a cortical defect model which blocked uninjured marrow from reaching the defect. Without the presence of marrow, the cortical defects ability to regenerate was significantly impaired. This implies that the marrow is important for cortical bone healing.

In conclusion, cancellous bone healing is different from its cortical counterpart and the general perception of fracture healing. We have briefly discerned healing mechanisms in cancellous bone that might be of clinical importance: the restricted cancellous bone formation is something to take into consideration when performing arthrodeses; and importance of marrow in skeletal defects (e.g. pseudarthroses). With this thesis, we hope to promote that further investigating on cancellous bone healing is necessary.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. p. 24
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1652
National Category
Orthopaedics Nursing Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:liu:diva-152349 (URN)10.3384/diss.diva-152349 (DOI)9789176851777 (ISBN)
Public defence
2018-12-06, Belladonna, Campus US, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2018-10-30 Created: 2018-10-29 Last updated: 2019-09-30Bibliographically approved
Bernhardsson, M. & Aspenberg, P. (2018). Osteoblast precursors and inflammatory cells arrive simultaneously to sites of a trabecular-bone injury. Acta Orthopaedica, 89(4), 457-461
Open this publication in new window or tab >>Osteoblast precursors and inflammatory cells arrive simultaneously to sites of a trabecular-bone injury
2018 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 89, no 4, p. 457-461Article in journal (Refereed) Published
Abstract [en]

Background and purpose - Fracture healing in the shaft is usually described as a sequence of events, starting with inflammation, which triggers mesenchymal tissue formation in successive steps. Most clinical fractures engage cancellous bone. We here describe fracture healing in cancellous bone, focusing on the timing of inflammatory and mesenchymal cell type appearance at the site of injury. Material and methods - Rats received a proximal tibial drill hole, A subgroup received clodronate-containing liposomes before or after surgery. The tibiae were analyzed with micro-CT and immunohistochemistry 1 to 7 days after injury. Results - Granulocytes (myeloperoxidase) appeared in moderate numbers within the hole at day 1 and then gradually disappeared. Macrophage expression (CD68) was seen on day 1, increased until day 3, and then decreased. Mesenchymal cells (vimentin) had already accumulated in the periphery of the hole on day 1. Mesenchymal cells dominated in the entire lesion on day 3, now producing extracellular matrix. A modest number of preosteoblasts (RUNX2) were seen on day 1 and peaked on day 4. Osteoid was seen on day 4 in the traumatized region, with a distinct border to the uninjured surrounding marrow. Clodronate liposomes given before the injury reduced the volume of bone formation at day 7, but no reduction in macrophage numbers could be detected. Interpretation - The typical sequence of events in shaft fractures was not seen. Mesenchymal cells appeared simultaneously with granulocyte and macrophage arrival. Clodronate liposomes, known to reduce macrophage numbers, seemed to be associated with the delineation of the volume of tissue to be replaced by bone.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2018
National Category
Orthopaedics
Identifiers
urn:nbn:se:liu:diva-150316 (URN)10.1080/17453674.2018.1481682 (DOI)000439704100018 ()29865916 (PubMedID)
Available from: 2018-08-16 Created: 2018-08-16 Last updated: 2019-05-02
Sandberg, O., Bernhardsson, M. & Aspenberg, P. (2017). Earlier effect of alendronate in mouse metaphyseal versus diaphyseal bone healing. Journal of Orthopaedic Research, 35(4), 793-799
Open this publication in new window or tab >>Earlier effect of alendronate in mouse metaphyseal versus diaphyseal bone healing
2017 (English)In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 35, no 4, p. 793-799Article in journal (Refereed) Published
Abstract [en]

Healing of injured cancellous bone is characterized by a transient stage of rapid bone formation throughout the traumatized bone volume, often followed by similarly rapid resorption. This is different from the slower diaphyseal healing via an external callus. We, therefore, hypothesized that antiresorptive treatment might have an earlier positive effect in cancellous bone healing than in diaphyseal fractures. One hundred and twenty-three male C57bl6 mice received either an internally stabilized diaphyseal osteotomy of the femur or a screw inserted into the tibial metaphysis. The mice were randomized to daily alendronate injections (200 μg/kg/day), or control injections, and killed for mechanical testing after 14, 21, or 28 days. The hypothesis was tested by a three-way Anova (time, site, and drug). The ultimate force was increased by bisphosphonate treatment in both models. There was a significant interaction between time, site, and drug (p < 0.001) so that the full positive effect of alendronate was evident in the metaphysis at 14 days, but first after 28 days in the diaphysis. While the early effect in the metaphysis might be translated into earlier healing, the late effect in the diaphysis was due to delayed remodeling of the callus, which might have less clinical importance. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
fracture, bisphosphonate, metaphysis, cancellous bone, trabecular bone, alendronate
National Category
Clinical Medicine Orthopaedics Nursing
Identifiers
urn:nbn:se:liu:diva-130921 (URN)10.1002/jor.23316 (DOI)000399728400008 ()27233101 (PubMedID)
Funder
Swedish Research CouncilLinköpings universitetÖstergötland County CouncilEU, FP7, Seventh Framework Programme
Note

Funding agencies: Swedish Research Council [VR 02031-47-5]; Linkoping University; Ostergotland County Council; European Communitys Seventh Framework Programme [FP7/2007-2013]

Available from: 2016-08-31 Created: 2016-08-31 Last updated: 2018-05-03Bibliographically approved
Bernhardsson, M., Sandberg, O. & Aspenberg, P. (2015). Anti-RANKL treatment improves screw fixation in cancellous bone in rats. Injury, 46(6), 990-995
Open this publication in new window or tab >>Anti-RANKL treatment improves screw fixation in cancellous bone in rats
2015 (English)In: Injury, ISSN 0020-1383, E-ISSN 1879-0267, Vol. 46, no 6, p. 990-995Article in journal (Refereed) Published
Abstract [en]

Bisphosphonates improve implant fixation in randomised clinical trials of knee prostheses, hip prostheses and dental implants. However, a limited amount of bone resorption is required for bisphosphonates to exert an effect. Anti-RANKL treatment does not have this limitation, and we therefore tested whether if they might be more effective for improvement of implant fixation. This is of interest, as anti-RANKL treatment with denosumab is now in common clinical use. Male SD rats received a stain-less steel screw in the right proximal tibia and a drill hole in the left (n = 42). They were randomised to subcutaneous injections of either alendronate (20 mu g/kg/day), alendronate (200 mu g/kg/day), osteoprotegerin with an Fc tag (OPG-Fc; 8 mg/kg, twice weekly), or saline control. After 4 weeks, the fixation of the steel screw was measured by pull-out test. The tibia with the drill hole was evaluated with mu CT. OPG-Fc increased the pull-out force compared to saline controls by 153% (p less than 0.001). There was no significant difference between OPG-Fc and the alendronate groups. OPG-Fc increased the bone density (BV/TV) in the previous drill hole compared to controls 7-fold (p less than 0.001). This increase was higher than with any alendronate dose (p less than 0.001). OPG-Fc increased the bone density of the L5 vertebral body, but there was no significant difference between OPG-Fc and alendronate. Our results suggest that screw fixation in cancellous bone can be dramatically improved by an antiRANKL agent. The effect was comparable to very high bisphosphonate doses. Screw insertion in cancellous bone elicits a metaphyseal fracture healing response, and our findings might be relevant not only for implant fixation, but also for fracture healing in cancellous bone.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Antiresorptives; Denosumab; Bisphosphonates; Rat model; Implant fixation; Fracture healing
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-119239 (URN)10.1016/j.injury.2015.02.011 (DOI)000355018800009 ()25744169 (PubMedID)
Note

Funding Agencies|Swedish Research Council [2031-47-5]; AFA Insurance company; European Union 7th framework programme (FP7) [279239]; Linkoping University

Available from: 2015-06-15 Created: 2015-06-12 Last updated: 2017-12-04
Bernhardsson, M., Sandberg, O. & Aspenberg, P. (2015). Experimental models for cancellous bone healing in the rat Comparison of drill holes and implanted screws. Acta Orthopaedica, 86(6), 745-750
Open this publication in new window or tab >>Experimental models for cancellous bone healing in the rat Comparison of drill holes and implanted screws
2015 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 86, no 6, p. 745-750Article in journal (Refereed) Published
Abstract [en]

Background and purpose - Cancellous bone appears to heal by mechanisms different from shaft fracture healing. There is a paucity of animal models for fractures in cancellous bone, especially with mechanical evaluation. One proposed model consists of a screw in the proximal tibia of rodents, evaluated by pull-out testing. We evaluated this model in rats by comparing it to the healing of empty drill holes, in order to explain its relevance for fracture healing in cancellous bone. To determine the sensitivity to external influences, we also compared the response to drugs that influence bone healing. Methods - Mechanical fixation of the screws was measured by pull-out test and related to the density of the new bone formed around similar, but radiolucent, PMMA screws. The pull-out force was also related to the bone density in drill holes at various time points, as measured by microCT. Results - The initial bone formation was similar in drill holes and around the screw, and appeared to be reflected by the pull-out force. Both models responded similarly to alendronate or teriparatide (PTH). Later, the models became different as the bone that initially filled the drill hole was resorbed to restore the bone marrow cavity, whereas on the implant surface a thin layer of bone remained, making it change gradually from a trauma-related model to an implant fixation model. Interpretation - The similar initial bone formation in the different models suggests that pull-out testing in the screw model is relevant for assessment of metaphyseal bone healing. The subsequent remodeling would not be of clinical relevance in either model.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2015
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-123812 (URN)000365484500019 ()26200395 (PubMedID)
Note

Funding Agencies|Swedish Research Council [2031-47-5]; AFA insurance company; EU [279239]; Linkoping University; Eli Lilly and Company

DOI does not work: 10.3109/17453674.2015.1075705

Available from: 2016-01-11 Created: 2016-01-11 Last updated: 2018-10-29
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